Cnet: Ten years after its release, Microsoft's Windows XP is still the most popular operating system in the world. The latest report from NetApplications shows that XP's market share slipped slightly in February, from 47 percent market share to 45 percent, but that wasn't enough to remove it from first place. Microsoft's Windows 7 picked up most of the users XP lost, climbing from a 36 percent share in January to 38 percent last month.